The present invention relates to a method for manufacturing circuit boards; more particularly the present invention relates to a method of manufacturing inspecting and calibrating circuit boards which control displayed numerals in a digital display device.
Digital display devices are commonly used in many types of equipment. One example where such displays are used is with a temperature controlled soldering iron wherein the temperature of the soldering iron is displayed as a digital readout. In such applications, electrical power is supplied to a control box. The control box both sends electrical power to the soldering iron and receives electrical signals from the soldering iron indicative of temperature. These received electrical signals are used to control the supply of electrical power to the soldering iron and may also be displayed digitally.
The control of the actual numerals and light quality of digital displays is accomplished by board mounted circuitry including an analog-digital converter. Such circuitry also includes a precisely controlled electrical resistance. In order to have a desired value of the displayed numerals the analog-digital converter must be calibrated. In order to have the proper quality of video display, it is necessary that the displayed numbers are proper and that the various illuminated light bar segments which make up the numbers in the video display have the proper tilt, midpoint and brightness. Heretofore the accuracy of the displayed numerals and the correction of tilt, midpoint and brightness, if done at all, was accomplished by manual methods wherein the precisely controlled resistance on the circuit board was manually tuned until the desired numerals and the tilt, midpoint and brightness of the displayed bar segments was obtained. This procedure was slow and expensive in that it was done manually.
There is therefore a need in the art to provide a system for automatically observing displayed numerals in a digital display device and measuring the tilt, midpoint and brightness of the numbers in a digital display and automatically calibrating the resistance in the control circuitry.